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Trypanosomosis

Zoonotic Potential

By the mid 1990s, it was estimated that Chagas disease (Trypanosoma cruzi) had affected between 16 and 18 million people, that 50 million were at risk, and that up to 30% of those infected would develop the chronic disease, with a fatal outcome (Moncayo, 1992; Wanderley and Correa, 1995). The geographical distribution of the disease, only existing in the Americas, is from 42° N latitude in the US (from California to Maryland) to approximately 34° S in Chile and 42° S in Argentina. Some 150 mammal species are susceptible to T. cruzi, with dogs, cats, rodents, and both domestic and wild lagomorphs constituting an important reservoir for human infection.

It is generally believed that T. cruzi infection is asymptomatic in wild animals, possibly due to lack of detailed clinical examination. In dogs, cardiac changes have been documented (Blandon et al., 1995). Dogs with acute experimental infections have exhibited alterations in the neurons of the Auerbach’s plexus and myositis in the lower third of the esophagus (Caliari et al., 1996). The chronic form in dogs is, as in man, characterised by myocarditis. Occasional reports of alterations in the brain and the peripheral nerves during the acute and chronic phases in dogs have also been recorded.

Several studies have shown that one of the major risk factors for T. cruzi infection in humans is the presence and number of dogs in the home (Acha and Szyfres, 2003). This observation would indicate that dogs are an important source of food and infection for the vectors (Gürtler et al., 1998), thus, participating in the zoonotic cycle of transmission of T. cruzi.